Don't shoot it?
Well, if you must then you must, but if you don't abuse it and don't carry it on a daily basis in a holster the finish should always be shiny. I only have two nickel guns presently, I used to collect nickel guns but I stopped, and one of them is very worn and "unshiny" because it was a daily carry gun for a Wells Fargo guard. The other is spectacularly shiny because I don't shoot it (I have, but I don't make a habit of it) and I do not abuse it nor do I carry it despite being a major fan of carrying 2" K frames.
I hope the photos show the difference clearly.